After four strong signals were heard last week, no new electronic pings have been detected since Tuesday, April 8th, in the search for the missing Malaysia Airlines jet. This means (or, keeping in line with nearly every new piece of information about the missing flight: could mean) that the black box's batteries have finally died.

The final ping was detected on Tuesday by a U.S. Navy device dragged by an Australian ship. Aviation expert Geoffrey Thomas spoke with the AP about the possibilities:

"We're now into Day 37 of this tragedy. The battery life on the beacons is supposed to last 30 days. We're hoping it might last 40 days. However, it's been four or five days since the last strong pings. What they're hoping for is to get one more, maybe two more pings so they can do a triangulation of the sounds and try and narrow the (search) area."

Once officials are sure that no more sounds will be discovered, a robotic submersible will be sent down to search for wreckage. But for now, despite a lack of pings to go on, air and sea crews continue to search in the southern Indian Ocean for debris and any sounds that could still be heard.